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September 7, 2010

Backstabbing Bacteria: A New Treatment For Infection?

by Sam Savage

Selfish bacterial cells that act in their own interests and do not cooperate with their infection-causing colleagues can actually reduce the severity of infection.

The selfish behavior of these uncooperative bacteria could offer a new hope in the future fight against antibiotic resistant infections such as MRSA, according to a study carried out by researchers at The University of Nottingham.

Bacteria work together by using a well-studied communication system called Quorum Sensing (QS). During infection, bacteria talk to each other using QS to coordinate the release of toxins.

Researchers at the University, led by Dr Steve Diggle in the Centre for Biomolecular Sciences, have discovered that in Staphylococcus aureus infections, bacteria defective in QS can benefit from 'opting out' of toxin production. By doing so, they can invest more energy in reproducing "” while taking advantage of the nutrient-rich infection maintained by their neighbors.

By looking after themselves in this way, QS-deficient bacteria are quickly able to outnumber other bacteria that are busy making toxins. As a result, the overall severity of infection is reduced as fewer toxins are produced.

"This opens up the interesting possibility of using these uncooperative bacteria to treat infection," said PhD student Eric Pollitt, who conducted the experimental work for the research and will present a paper on the study at the Society for General Microbiology's autumn meeting today (Sept 6).

The Nottingham group tested the theory by introducing S.aureus into waxworms that subsequently developed infections.

"We found that the QS-deficient bacteria could not only outgrow normal bacteria in the same population, but that they could also invade other cooperating populations to reduce the severity of infection. This means that we could potentially isolate QS-deficient bacteria and use them to treat clinical S.aureus infections," he added.

New approaches for the treatment of S.aureus infections are desperately needed as many strains of the bacterium such as Methicillin-resistant Staphylococcus aureus (MRSA) are resistant to antibiotics. "Importantly, as any treatment involving QS-deficient bacteria would not be based on antibiotics, it could complement current treatments for S. aureus infections," said Mr Pollitt.

Using bacteria to treat bacterial infections is a potentially useful, yet paradoxical approach. "It's an interesting concept of 'fighting like with like'", suggested Mr Pollitt. "This work highlights that the interactions between bacteria during an infection can be just as important as the interactions between the bacteria and the host."